1. Field of the Invention
The present invention relates to a fuel cell system provided with a fuel cell. This fuel cell system is suitable for use in a traveling power source of an electric vehicle or the like, or a stationary power source.
2. Description of the Related Art
As the fuel cell, there are a phosphoric acid fuel cell, a fused carbonate fuel cell, a solid-electrolyte fuel cell, an alkaline fuel cell, and a polymer electrolyte fuel cell. For example, the polymer electrolyte fuel cell (PEFC) includes a hydrogen electrode (anode electrode) to which a gas containing hydrogen is supplied, an oxygen electrode (cathode electrode) to which an oxygen gas containing oxygen, such as air, is supplied, and a solid polymer film type electrolyte layer made of ion exchange resin held between the hydrogen electrode and the oxygen electrode. A catalyst such as platinum is supported in the electrolyte of the oxygen electrode and the electrolyte of the hydrogen electrode.
In these fuel cells, a fuel chamber for supplying hydrogen in the gas to the hydrogen electrode is formed, and a gas supply port for supplying the gas and a gas discharge port for discharging the gas are formed in the fuel chamber. Besides, in these fuel cells, an oxygen chamber for supplying oxygen in the oxygen gas to the oxygen electrode is formed, and an oxygen gas supply port for supplying the oxygen gas and an oxygen gas discharge port for discharging the oxygen gas are formed in the oxygen chamber.
In the fuel cell system provided with the fuel cell, the oxygen gas is supplied into the oxygen chamber of the fuel cell through the oxygen gas supply port, while the gas is supplied into the fuel chamber of the fuel cell through the gas supply portion, whereby a reaction ofH2→2H++2−etakes place at the side of the hydrogen electrode. H+generated here moves in the form of H3O+ through the electrolyte layer, and a reaction of(½)O2+2H++2e−→H2Otakes place at the side of the oxygen electrode. In this way, an electromotive force due to an electrochemical reaction ofH2+(½)O2→H2Ois obtained between the hydrogen electrode and the oxygen electrode. Besides, produced water is generated by this at the side of the oxygen electrode. Then, an exhaust gas in the oxygen chamber of the fuel cell in which oxygen is not consumed, together with the produced water and the like, is discharged from the oxygen gas discharge port, while the gas in the fuel chamber in which hydrogen is not consumed, together with the produced water and the like, is discharged from the gas discharge port.
Now, for example, immediately after stopping of the fuel cell, the hydrogen gas remains in the fuel chamber. In case this state is left as it is, air is mixed into the fuel chamber from the outside, and the hydrogen gas and the oxygen gas are mixed.
Besides, at the time of start-up of the fuel cell, the air exists in the fuel chamber, and when the hydrogen gas as the fuel is injected in this state, the hydrogen gas and the air (oxygen gas) are mixed. It is known that deterioration of a catalyst at the side of the oxygen electrode can occur by the mixture of the hydrogen gas and the oxygen gas.
Then, it is conceivable that a suction device for sucking a gas from the gas discharge port of the fuel chamber is provided, and the remaining gas is discharged to the outside of the fuel cell to prevent the mixture of the hydrogen gas and the oxygen gas.
In this case, there occurs a problem of how to construct the suction device and how to use it.